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Development of Fire-Free, Long-Lasting, Water-Based Battery for ESS

New and renewable energy sources, such as sunlight and wind power, are drawing attention in response to climate change. The utilization of new and renewable energy sources demands that their intermittency be overcome by storing power in Energy Storage systems (ESS). Lithium ion battery-based ESSs, currently used in power plants, often suffer fire accidents due to battery characteristics.

To solve the problem, Professor Hee-tak Kim’s group has conducted a study to improve an essentially incombustible material. The zinc/bromine redox flow battery that his group studied is basically free from fire risk, and employs a material that is cheaper than the materials required by lithium ion batteries. The group has developed elemental technology needed to establish ESS, and will conduct follow-up studies to fabricate a large-area prototype and establish the relevant system, contributing to the safe supply of new and renewable energy sources and ESS.

Solution to intermittency issue of power generation depending on weather conditions

About 90% of currently used ESSs are lithium ion batteries, and water-based or sodium sulfur batteries account for the remaining portion. However, ESSs based on lithium ion and sodium sulfur batteries have a flammability problem that can cause power plants to stop operating repeatedly due to fire accidents. On the other hand, water-based batteries, such as vanadium redox and zinc bromine batteries, are nonflammable. In particular, zinc bromine batteries employ as active material zinc bromide, which is inexpensive, and thus has high applicability among various water-based redox flow
batteries. In addition, zinc bromine batteries have other advantages, including high operation voltage and high energy density. Since zinc metal forms ‘dendrites,’ which are uneven bumps, in the charge/discharge process, the battery lifetime is short due to internal short-circuits occurring in the battery.

Development of technology for suppressing zinc dendrite to address lifetime issue of zinc bromine battery

Professor Hee-tak Kim’s group has developed a technology for suppressing zinc dendrite to address the lifetime issues of zinc bromine batteries. The group investigated the zinc electrode deterioration mechanism and prevented the formation of dendrites to develop a zinc-based redox flow battery that has the longest lifetime in the world. The research has presented the possibility of developing next-generation water-based batteries by removing the risk of fire by employing a fire-free water-based electrolyte and overcoming the lifetime limitation.

The research group noted that ‘self-aggregation’ occurs through ‘surface diffusion’ of zinc nuclei on the carbon electrode surface, which has low surface energy. After learning that surface aggregation of the zinc nuclei is the cause of the dendrite formation, the group found that the dendrite formation may be prevented by suppressing the surface diffusion of zinc nuclei in a specific carbon defective structure. A carbon electrode having such characteristics was applied to a zinc bromine redox flow battery to develop a water-based battery that has a charge/discharge current density about 30
times higher than that of lithium ion batteries and that may be repeatedly used for more than 5000 charge/discharge cycles.

Professor Kim stated, “Our goal is to develop a full ESS by completing the various element technologies for ESS batteries. We will fabricate and verify a prototype at KAIST by 2024 to increase the utilization of new and renewable energy sources and contribute to the supply of safe ESS.” The results of the
study were published as a front cover article of the journal Energy and Environmental Science (IF=30.289), and applications have been filed for Korean and international patents.

Prof. Hee-tak Kim
2020 KI Annual Report

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